PEMs, such as polymer electrolyte membranes, are utilized to transport protons between the anode and cathode. Commercially available conventional PEM are composed generally of an ionomer, usually a polymer with a fluoro-polymer backbone with pendants carrying an ionizable moiety like sulfonic acid groups. There are many variations and commercial products available. One of the well-known examples of the commercial PEM is NAFION.
Typically, fluoropolymer based PEM encounter many failure modes leading to lower operational life and a lower operational temperature around 80° C., and are thus prone to carbon monoxide poisoning. Major failure modes include water management issues like flooding, dry-out, poor dissipation of the heat generated, mechanical failures like pin-holes or ruptures and electro osmatic drag arising from concentration polarization.